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I think I'm happy about that. I think chains are more durable and have the advantage of not having to be sealed by a silly over $200 set of plastic covers that get in the way of any real engine work. Also, chains stretch less so that when you first romp on the throttle, especially with modded cars that have lots of power, the elastic belt stretches for an instant and timing gets stretched out and is wrong for an instant. The timing is probably less than a degree off with sane powerlevels (like our sub-350 hp levels). With a chain, it takes probably 3 or 4 times that power to get any kind of elastic response from the metal or the tensioning system, be it hydraulic or otherwise.

Downside is what? Why not use chains instead of belts?

Just curious and wanted to stir up some opinions. I know on the ultra high hp american cars, almost everyone gets rid of the chains because of the aforementioned stretching and replaces the chain with mechanical gears (noisy, so never included in OEM setups)...

Joel

[This message has been edited by Joel Gat, 1.8L (edited October 16, 2000).]

Colin, the H6 might very well have plastic everywhere. Plastic is like the OEM version of stickers for rice/wheat/whatever-boys. The more they put on the cars, the happier they seem to be. However, the biggest function of that plastic cover on our cars is to keep anything from getting on the belt since anything, especially oil, but including coolant, can degrade the rubber or induce slipping and cause a fatal engine death

With a chain, you don't have to worry about that kind of crap. There's still a cover, but you don't have to have something like 20 gaskets included with the cover (which I had the pleasure of figuring out recently when I rebuilt an engine and needed to replace that cover).

Weight is a good point, though. I guess that's another reason to avoid chains on low torque cars like 4-bangers and why it's okay to use them on the H6.

Anyone else read the article in automotive engineering? They seem to love new engines and always yap on forever about every new feature

My girlfriend has a Saturn SC2 which has a chain. It's significantly faster than my OBS and the engine seems to be more flexible overall even though it doesn't have as much torque, although a lot of it may be because it's a lighter car.

I think it was rated at 8.5 seconds to 60 which is pretty good for a 4 cylinder with a chain. I've always wondered if Subie engines would do well without belts since they're such a pain in the butt to change.

Assuming this is correct, a thinner/skinnier belt means the total overall length of the block may be shorter. Maybe this is part of the reason why Subaru was able to make the EJ30 (?) block only 25mm longer than the EJ25. Who knows? *shrug*

That's interesting that Subaru decided to use a timing chain on the new H6. Joel, you mentioned the problem of belt/chain slack on the timing. It's interesting to note that the H6 for the SVX does not use belts OR chains to control the timing of the cams! Yup, you guessed it -- it uses gears, but not just any gears -- Subaru used scissor gears to minimize the "slack/space" between the gears so that timing would be nearly perfect!

How do I know this? Well, my cousin owns an SVX - a '92 I believe, and he also has the coin to dish out for a set of Subaru maintenance manuals. He's big into the tech side of anything (cars, computers, AV equipment, etc.) and he mentioned to me about the engineering that Subaru put into the timing mechanism!

I guess the scissor gear mechanism was just a little too expensive for the latest incarnation of the H6. It'll be interesting to see what people do to the new one though!

Timing chains are narrower. They do strech less, but there are problems with tensioning them and chain slap that offset this. The extra mass is of minimal effect, since you can reduce rotating mass on the flywheel or crank pulley to compensate.

Subaru really need to do ALL timing off a direct crank trigger(s) this will lead to perfect timing and minor cam timing differences will not have that large of a effect compared to missed ignition of fuel injector timing.

The timing belt covers are really there only to keep large objects (bigger than dust) out of the timing belt. Atleast on the old SOHC 2 valve motors both the WP, and oilpump can leak right on to them as the WP is above a low spot in the cover, and the oilpump is behind the cover. I ran my old turbo for a long time w/o the covers with no problem. The 6cyl will have them only becasue the dipstick bolts to the center cover, and the passenger side one is needed to keep wires out of the pulley.

Uhh, timing as in valve timing, not ignition timing The chain/belt directly turns the cams in an overhead cam setup. The ignition timing is done by various methods like crank trigger, cam trigger, etc.

Hate to disagree, but valve timing IS critical. Think about how much variation in terms of time even .5 degrees early or late is. It's thousands of a second, in the scale of an event of hundredths of a second...it is significant. I had built drag motors (Kawasaki, motorcycle stuff) and setting the cam timing between races was a real difference in performance.

Belts stretch very little at these power levels as Joel suggests. The tiny little bit of 'give' in the belts helps to absorb the very slight uneveness in crank rotation caused by the crank throws not being at a perfect 180 degrees, the slight wobble from torsional vibration, the cylinder bores not being perfectly parallel and other effects. With gear and (to a lesser extent) chain drives, these irregularities are transmitted to, and affect the valve motion.

Boy, working 14 months on co-op with timing chains I would have thought I could think of more advantages, but I can't. A timing chain system is more complex than belt from the examples I have seen. You will need an arm, guide and tensioning device on each bank to help control chain movement. About 95% of the time the tensioner is hydraulic, which will mean less oil to engine, and to variable cam timing devices as well. The front cover will have to have be able to seal the oil against the block since there is a lot of oil flying around in there. Chains can be pretty thin, but compared to a belt I don't think you are saving that much room. They are strong though, and I wouldn't mind having that peice of mind in an engine. I got a lot of parts back at work that I inspected with 100,000+ miles that were in great shape. Chains are also going to wear over time putting metal into the oiling system. I know that it isn't that much and will be filtered out, but there is that disadvantage. Designed properly, a timing chain won't have that much noise, but this also takes into consideration the front cover which usually acts like a speaker to amplify any noise made by the system. Despite what sounds like a discouraging post here, I think I would rather have a timing chain than belt. Longer life, better strength and a little more piece of mind for a stressed engine such as a Turbo RS.

I just thought I would metion that I went to a meeting about the H6 today and go to see it out of the car and all sliced up. The chaince is enclosed in a metal housing in the front of the engine and looks like it is pretty well sealed about a scew holding the cover on every 1/2 inch I don't think they exspect anyone going in there. Also they had the Porche boxter engine there they use belts on that one just thought I would mention it. It was very intresting comparing the two engines especailly where the subaru was only 8hp less.
Joshua
MY98 RS
Subaru Salesman

Here's a thought RE the durability of a chain vs. the durability of a belt.

On a high-milage engine, the belt will have been replaced, probably several times. Thus, the timing will be as precise as it was when it was new (minus valve/cam wear). In a high-milage engine with a chain, the chain wear will have accumulated, throwing off the timing more and more.

My thought is that it kind of offsets the durability advantage, since the belts are cheap and easy(ier) to replace. Of course, I've never heard of anybody breaking a chain and smacking a valve. I've heard of quite a bit of that with belts.

Chains don't really continue to wear. Most of the elongation that happens is when the engine is new. After that the wear tapers off and is only slight for the rest of the engine's life. When designing the system, the chain is initially just a tad short to take into consideration the initial break-in. This isn't saying that when someone doens't change the oil for 20K miles that chain elongation won't occur.....you gotta take care of things. I have seen plenty of chains that were high mileage that were in almost new shape

I recently talked to a sube tech that went to school to see the H6 engine...one thing he noticed was the timing covers. He said there were like 40 bolt holding on the single cover (not like the three piece cover used on ours) and that the bolts were all different sizes and some were hex heads. Behind this cover was another cover allowing you to get at the oil pump and the water pump... but this cover had another 30 some bolts. His overall impression of the H6 wasn;t great. He said it reminded him a bit of BMW design= pain in the ass to werk on. He also said that Subaru seems to have changed everything that werked well seeminly just so they could do something new. He isn;t excited about werking on them... He said the pick up was great powerwise,.. a little more torquey off the line. I didn;t really press him for more info since I'm not really excited about getting a Legacy wagon... but if you have anymore questions that you would like me to ask him then let me know... [email protected]

Chains - less compromised. Noisier, but largely maintenance-free (unless you own an M car, in which case, a new chain every 100k miles is a good insurance policy). Chains are also thinner, unless you have an enormous duplex chain a la BMW 1.8/1.9 16v four, which is very wide (and noisy, too).

Belts? Quieter, simpler, cheaper, but need replacing. So the servicing costs are higher (you pay through servicing rather than through list price - nothing comes for free!).

Isn't the whole point for Subaru going w/ a timing-chain is to make life more simple for its customers? But isn't there a huge pitfall that Subaru is facing with the decision to start using a chain?
1) A chain on high production low cost cars is great for the average driver. IF the head gaskets never "pop".
But isn't the problem that all and I do mean all, 2.5 Subaru engines will pop a head gasket by 175k mi tops. I've owned 25 or 30 Subaru's from 1.8's to 3.3's and I swear it's a fact with every 2.5 no matter what "upgraded" head gaskets are used. Every engine they make except the 1.8 and maybe the 2.0 will eventually need a headgasket job. Heaven knows, that for any semi-knowlegable shade tree type person, doing a head gasket job on a Subaru is just no big deal. In fact it's kind of fun (except for the DOHC's anyway).
But I believe Subaru is going to start to see a real resale problem 6-8 years.
Because: no matter what Subaru says, their 2.5 engines will continue to pop head gaskets. No matter what they say or what changes are made, by about 175k mi pretty much every one will need a head gasket job.
Given that as a fact (and I'm sure this will generate many people on this forum who think Subaru has solved their H-G problem, but I'm equally sure that I'm going to be proven correct. And when the inevitable happens, and the bubbles start to come up through the radiator...then the new timing-chain engines will be a real bear to fix.
What was once an enjoyable afternoon repair (and a low cost fix) that assures our trusted "subi's" will hit 300k w/o anything else major happening, it will now become a real b--tch. A pain to work on, and much more costly.
Subaru's argument will be "We've fixed the head gasket trouble". Their argument will continue with "and now your Subaru will last 300k with no timing belt worries... heck Subaru has done you a favor!"... If it were really true I'd buy one right now, but I seriously doubt it.
Reality will dictate that this is just not true. H-G's will continue to blow, and what was once a fun quick nd simple job will become a nightmare.
What was once a fun engine to work on will become just another over engineered, needlessly complicated piece of machinery that just isn't fun to work on anymore.
But we should try to look on the bright side. Older Subrus with belts will be worth more in the used-car market. And for the next 15 years there will still be plenty of them available.
And then the inevitable will happen: either Subaru will go back to belts as Coke went back to the original flavor... or people will abandone their favorite snow car and start buying the brand that gives us an honest product at an honest price.
If any Subaru engines really do prove themselves as "head gasket proof"... as being able to hit 325-350k mi (right where even well designed t-chains usually wear out) then I will keep buying Subarus and applaud Subaru for taking the "bold"step into chains. But my money is on the fact that their head gaskets will continue to keep popping at 150-175 no matter what they do. My money is on the fact that this will prove to be a very bad decision in the long run.
Hope I'm wrong! I sure like Subaru's, both for their "snowworthyness", and for their ease of repair and reliability. I'm just afraid this move will pull the rug out from under half the reason we buy them.

Thank goodness you bumped an 11-year-old thread to make baseless claims about an engine nobody has seen yet. Be sure to check back into this thread about 15 years from now when the '12 models are starting to reach 300k miles and let us know how you think things have turned out!!